50 



Nests of the following species are found on 

 Wild Horse Island near the S, spaldingii sites. 



Haliaeetus leucocephalus (bald eagle) - 

 listed as "endangered" in Montana (S2) by 

 The Montana Natural Heritage Program. 



Population biology of the taxon. 



A. General summary: Ten populations of Silene 

 spaldingii occur in northwest Montana in Palouse 

 prairie areas. Populations are separated by 

 approximately 88 miles. The largest population 

 occurs in the Tobacco Valley, and consists of 10,000 

 plants in two subpopulations . The largest 

 population in the Niarada/Flathead Lake vicinity 

 contains 250 plants. Other populations have less 

 than 100 plants, and most have less than 30. Silene 

 spaldingii is thought to be an obligate or near- 

 obligate outcrossing species (Lesica, 1988); see 

 Appendix C, p. 70, for more detailed information. 

 Bumblebees (Bombus sp.) are among the known 

 pollinators (Lesica, 1988) ; see Appendix C. 



B. Demography. 



1. Known populations: There are currently eight 

 known populations of S. spaldingii in Montana: 

 two populations in the Tobacco Valley (Lincoln 

 County) , five in the vicinity of Niarada, 

 Montana (Sanders and Flathead counties) , and 

 one on Wild Horse Island in Flathead Lake (Lake 

 County) . This species is also currently known 

 from fifteen sites in Washington and two in 

 Idaho. 



2. General demographic details (Montana): 



a. Dancing Prairie-Tobacco Plains South (001) 



1. Area occupied by population: ca. 200 

 acres. 



2. Estimated number of individuals: ca. 

 10,000 plants in three 

 subpopulations . 



3. Density: Very localized areas have a 

 fairly dense cover of plants; however 

 most are scattered individuals. 



4. Presence of dispersed seeds: Unknown. 



5. Evidence of reproduction: Flowering 

 and fruiting plants and seed 

 production; see (Lesica, 1988) , 

 Appendix B, p. 69. 



